This invention relates to ducted rocket motors and distribution of compressible fluid fuel that issues from the gas generator of these motors. This invention, more specifically, relates to a fuel injector that distributes such fluid fuel flowing at widely varying rates among spaced discharge ports for use in a secondary combustor of the rocket motor. This invention, still more specifically, relates to such a fuel injector which has proportioned axial and radial fuel flow passages for delivering selected amounts of the variable rate fuel flow smoothly and regularly to the secondary combustor.
Fixed flow rate ducted rocket fuel injectors distribute among a plurality of spaced discharge ports compressible fluid fuel flowing at a constant rate between gas generator and secondary combustor sections of a ducted rocket motor. A fixed flow injector may be designed so that its discharge ports have a much smaller total effective area than the effective area of its upstream, axial flow passage. As a result, the flow splits among these discharge ports approximately in accordance with their respective relative areas.
Variable flow rate fuel injectors employ an upstream throttle device for control of flow rate through the fuel injector. The discharge ports of these variable flow injectors need to have a total effective flow area that equals or exceeds that of the throttle device throat at its maximum opening. Otherwise, there can be loss of throttling capacity at corresponding minimum flow rates.
In addition, if the internal flow of fuel in these variable rate fuel injectors is allowed to accelerate to supersonic, then loss of throttling capacity also can occur along with distorted fuel distribution as a result of local shock phenomena and sharply reduced port discharge coefficients.
In accordance with this invention a fuel injector is provided which permits smooth and regular discharge of a compressible fluid fuel flowing at widely varying rates between gas generator and secondary combustor sections of a ducted rocket motor without loss of throttling capacity of an upstream throttling device.
Further in accordance with this invention, the fuel injector has a design which allows fabrication using ordinary machining techniques.